This invention relates to the field of controlled release of active agents, controlled release compositions, methods, and articles which comprise such compositions. The need for the controlled and sustained release of an active agent into the environment exists in many fields, for instance, in residential and other consumer fields, in agriculture, and in telecommunications.
Matrices that have been used in monolithic controlled release formulations include plasticized polyvinylchloride, rubber (U.S. Pat. No. 3,318,769) and certain polyurethanes (U.S. Pat. Nos. 4,594,380 and 4,189,467). The rubber matrices typically are cured by conventional rubber chemistry, e.g., by sulfur vulcanization or by means of peroxides (U.S. Pat. No. 3,639,583). These curing processes typically comprise a high-temperature step. The high temperature step frequently is a complicating factor when active agents having relatively high vapor pressure, or active agents that are subject to deactivation at the elevated temperature, are to be incorporated into the matrix material. Forming a polyurethane matrix requires polyols to react with isocyanates. Unfortunately, many active ingredients for sustained release contain alcohol functionality which competes with such polyols in the curing reaction. As a result, the polyurethane gel formation is hindered in the presence of alcoholic active ingredients.
Because of the importance of controlled release of active agents, a controlled release system that does not have the shortcomings of prior art systems would be of substantial benefit.